See the following for more information:

Book List Grouping

To help organize book lists, you can choose to group items according to the following criteria:

When grouping is enabled, books are grouped according to the values of the book information criteria selected. Since books can have multiple Category and Author values, the same book may appear in more than one group. Books that do not belong in any group (because they are not part of a series, or are uncategorized, for example) are listed at the top level of the list below the category value folders.

Note the navigation (or "breadcrumb") bar that appears at the top of the list, just below the action bar. This identifies the grouping criteria and value applicable to the current list, and allows navigation back to the top level by tapping the link.

To change the grouping of a book list, select the "Display Options" item from a book list item context menu and select the grouping option you wish to use from the resulting dialog.

Display Options
1. Display Options
Select Group By Category
2. Select Group By Category
Grouped By Category
3. Grouped By Category
Books In Category
4. Books In Category
Select Group By Series
5. Select Group By Series
Grouped By Series
6. Grouped By Series
Books In Series
7. Books In Series
Select Group By Author
8. Select Group By Author
Grouped By Author
9. Grouped By Author
Books By Author
10. Books By Author
Select No Grouping
11. Select No Grouping
Ungrouped Book List
12. Ungrouped Book List